1. Field of the Invention
The present invention relates to a swash-plate-type compressor, preferably adapted for use in automobile air-conditioning systems, more specifically to a swash-plate-type compressor with a muffling arrangement for suppressing pulsation in discharge pressure of a refrigerant gas after compression.
2. Description of the Prior Art
Generally, in a swash-plate-type refrigerant gas compressor for use in automobile air-conditioning systems, refrigerant gas returning from the air-conditioning system is sucked into and compressed by a multi-cylinder compressing system having pistons operated by a single rotary swash plate. The refrigerant gas, when compressed, is discharged from the cylinder bores into discharge chambers provided at axially front and rear sides of a cylinder block unit of the compressor. The compressed refrigerant gas is then passed through discharged passageways of the cylinder block unit and is further collected together. Subsequently, the collected refrigerant gas is sent out through a connecting flange toward a cooling circuit of the air-conditioning system.
During the above-mentioned compressing and discharging of the refrigerant gas, there is pulsation in the discharge pressure of the gas due to the reciprocating motion of the pistons. The frequency of the pulsation depends on the number of the cylinder bores. The pulsation needs to be suppressed to prevent noise and vibration problems. Accordingly, a muffling chamber has conventionally been provided in the refrigerant-gas delivery circuit for reducing the pulsation in the discharge pressure of the refrigerant gas.
FIG. 1 illustrates a conventional case where a chamber 51 having a substantial volume is provided as a muffling chamber. The chamber 51 is provided in a connecting flange 50a for sending out the refrigerant gas after compression toward a cooling circuit of the air-conditioning system. The refrigerant gas after compression is once choked by orifices 53 and then flows into the muffling chamber 51 so as to suddenly expand. The refrigerant gas is then again choked by an orifice 54 prior to flowing into the cooling circuit. Thus, the sudden expansion and the double choking of the refrigerant gas contributes to suppression of the pulsation.
FIG. 2 illustrated another conventional case where a casing 50b is arranged in a delivery circuit 52. The casing 50b provides a muffling chamber 51 and two inlet and outlet orifices 53 and 54 for the refrigerant gas delivered from the compressor. Pulsation is similarly suppressed while the refrigerant gas, after compression, passes through the muffling chamber 51 and the orifices 53 and 54.
However, in the conventional arrangements of muffling chambers as shown in FIGS. 1 and 2, the suppressing efficiency of the pulsation as well as the suppressing frequency are determined by the ratio of the cross-sectional areas of the orifices and the muffling chamber and the length of the muffling chamber in the flowing direction of the refrigerant gas. Therefore, an extremely large volume muffling chamber is needed to obtain the necessary suppressing efficiency and suppressing frequency.
In order to eliminate the above problem, U.S. Pat. No. 3,785,751 to Nemoto et al discloses a silencing chamber formed on the cylindrical casing of a swash-plate-type compressor by means of a cover. In the compressor, the silencing action is obtained by a sudden change of volume of the compressed gas when the compressed gas enters into the silencing chamber. However, there is no teaching of any additional action to suppress the pulsation in discharging pressure of the refrigerant gas.